A lithium secondary battery, which basically employs lithium metal as the anode (negative-electrode) active material, develops highly-active arborescent lithium metal (dendrite) or mossy lithium metal (moss) during charge when the battery is repeatedly charged and discharged. There are cases where this dendrite or moss directly or indirectly, after falling from the anode (negative electrode), comes into contact with the cathode (positive-electrode) active material to cause an internal short-circuit. In this respect, lithium secondary batteries are fraught with an exceedingly serious danger. Although use of a lithium alloy with Al, Al-Mn (U.S. Pat. No. 4,820,59), Al-Mg (JP-A-57-98977), Al-Sn (JP-A-63-6742), Al-In, or Al-Cd (JP-A-1-144573) has been proposed as a measure for avoiding the occurrence of such a short-circuit, this is not an complete solution to the problem because lithium metal is still being employed. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) As an expedient in which lithium metal is not used, use of a calcined carbonaceous compound capable of intercalating and/or deintercalating lithium ions or lithium metal (e.g., JP-A-58-209864, JP-A-61-214417, JP-A-62-88269, JP-A-62-216170, JP-JP-A-63-13282, JP-A-63-24555, JP-A-63-121247, JP-A-63-121257, JP-A-63-155568, JP-A-63-276873, JP-A-63-314821, JP-A-1-204361, JP-A-1-221859, and JP-A-1-274360) has been proposed. However, such a battery disadvantageously has a reduced charge-discharge capacity because the carbonaceous compound employed therein does not directly take part in the charge and discharge reactions. Moreover, high-speed charging and discharging of these batteries is difficult, and the above expedient is not a complete solution to overdischarge, overcharge and safety concerns. A further defect of the battery employing such a calcined carbonaceous compound is that complete dehydration of the compound in battery fabricating is difficult because of the extremely large surface area of the compound. Hence, a further improvement is desired.
In "Batteries", edited by Shiroh Yoshizawa, published by Kodansha Scientific, Japan (1986), p. 148, a battery example is described which employs Li/Li.sub.2 SO.sub.4 as a negative electrode and bis(tetrabutylammonium) sulfate as an electrolyte. Essentially, it is disclosed therein that this battery contains two electrolytic solutions, and that the two electrolytic solutions should be prevented from mingling with each other, indicating that this battery is difficult to realize.
In the field of secondary batteries employing an organic electrolytic solution, incorporation of halide ions, sulfuric acid ions, carbonic acid ions, or the like in an electrolytic solution is disclosed, for example, in JP-A-60-249265 (bromine ions and/or iodine ions), JP-A-63-76274 (alkali metal fluoride ions), JP-A-2-114464 (alkali metal halide or other halide), JP-A-63-198295 (lithium sulfate), JP-A-1-286263 (lithium carbonate), and JP-A-63-313467 (lithium carbonate and calcium hydroxide). However, the batteries disclosed therein all employ a light metal, lithium metal, or a lithium alloy as the anode active material. Use of inorganic solid electrolytes including lithium halides and the like are disclosed in U.S. Pat. No. 3,615,828 and many others. However, none of the above references teach or suggest the novel construction and effects of the present invention.
Further, incorporation of a quaternary salt in an electrolytic solution (e.g., JP-A-49-10527 and JP-A-2-281572) has been disclosed. However, none of these references teach or suggest the novel construction and effects of the present invention.